The present invention relates to the discovery, identification, and characterization of novel human polynucleotide sequences and the novel polypeptides encoded thereby. The invention encompasses the described polynucleotides, host cell expression systems, the encoded proteins or polypeptides, fusion proteins including the encoded proteins or polypeptides, peptide fragments of the encoded protein or polypeptides, antibodies directed against the encoded proteins or peptides, and genetically engineered animals that lack the disclosed genes or over express the disclosed genes, antagonists and agonists of the proteins, and other compounds that modulate the expression or activity of the proteins encoded by the disclosed genes that can be used for diagnosis, drug screening, clinical trial monitoring, the treatment of physiological or behavioral disorders, or to otherwise improve a patient""s quality of life.
The body transports lipids by complexing the hydrophobic lipids with carrier lipoproteins that allow the lipids to circulate through the body. In the blood, lipids such as cholesterol are often found complexed within macromolecular assemblies of lipoproteins that have traditionally been categorized by density. The most abundant cholesterol transport lipoproteins are of the low density lipoprotein, or LDL, class. High circulating levels of LDL in the blood have been associated with, inter alia, atherosclerosis, heart disease, high blood pressure, and stroke.
The present invention relates to the discovery, identification, and characterization of nucleotides that encode novel human LDL receptor family genes, and the corresponding amino acid sequences encoded by the disclosed genes. The novel human LDL receptor family proteins (LDLPs) described for the first time herein share structural motifs found in mammalian LDL receptor proteins. Certain novel human nucleic acid sequences described herein respectively encode proteins of 345 and 161 amino acids in length (see SEQ ID NOS: 2 and 4).
A murine homologue of the described LDLPs has been identified and xe2x80x9cknockoutxe2x80x9d embryonic stem (ES) cells have been produced using the method described in U.S. application Ser. No. 08/942,806, and more specifically described in the publication xe2x80x9cMouse Mutagenesis,xe2x80x9d 1998, First Edition, Lexicon Genetics, Inc. both of which are herein incorporated by reference in their entirety. Alternatively, conventional methods for generating genetically engineered animals and cells can also be used (see, for example, PCT Applic. No. PCT/US98/03243, filed Feb. 20, 1998, herein incorporated by reference). Accordingly, an additional aspect of the present invention includes knockout cells and animals having genetically engineered mutations in the genes encoding the presently described LDLPs.
The invention encompasses the nucleotides presented in the Sequence Listing, host cells expressing such nucleotides, the expression products of such nucleotides, and: (a) nucleotides that encode mammalian homologues of the described genes, including the specifically described LDLPs, and related LDLP products; (b) nucleotides that encode one or more portions of a LDLP that correspond to functional domains (including, but not limited to, a extracellular or transmembrane domain, accessory protein/self-association domain, etc.), and the polypeptide products specified by such nucleotide sequences, including but not limited to the novel regions of any active domain(s); (c) isolated nucleotides that encode mutant versions, engineered or naturally occurring, of the described LDLPs in which all or a part of at least one domain is deleted or altered, and the polypeptide products specified by such nucleotide sequences, including but not limited to soluble proteins and peptides in which all or a portion of the signal sequence in deleted; (d) nucleotides that encode chimeric fusion proteins containing all or a portion of a LDLP, or one of its domains (e.g., a extracellular or transmembrane domain, accessory protein/self-association domain, etc.) fused to another peptide or polypeptide.
The invention also encompasses agonists and antagonists of the LDLPs, including small molecules, large molecules, mutant LDLPs, or portions thereof that compete with or bind native LDLP, antibodies that bind LDLPs, as well as nucleotide sequences that can be used to inhibit the expression of the described LDLPs (e.g., antisense, double stranded RNA, ribozyme molecules, and gene or regulatory sequence replacement constructs) or to enhance the expression of the described LDLPs (e.g., expression constructs that place a LDLP gene under the control of a strong promoter system), and transgenic animals that express a LDLP transgene, or xe2x80x9cknock-outsxe2x80x9d (which can be conditional) that have been engineered to not express a functional LDLP.
Further, the present invention also relates to methods for the use of the described LDLP products for the identification of compounds that modulate, i.e., act as agonists or antagonists, of LDLP expression and/or LDLP product activity. Such compounds can be used as therapeutic agents for the treatment of any of a wide variety of symptomatic representations of biological disorders or imbalances.
An additional embodiment of the present invention is therapy and treatments mediated by LDLP gene delivery. Gene delivery can be to somatic cells or stem cells, and may be effected using viral (i.e., retrovirus, adeno-associated virus, etc.) or non-viral (i.e., cationic lipids, formulations using xe2x80x9cnakedxe2x80x9d DNA, etc.) methods.